This invention relates to a method and a device for inspecting the sidewall of a bottle which detect defects on the sidewall of the bottle.
It is necessary to inspect glass bottles for liquors, beverages, foods, etc. which have been recovered for reuses or even those which are fresh from bottle forming devices. These bottles are inspected at portions, i.e., the bodies or sidewalls, bottoms, tops of the mouths, and threaded necks. Sidewalls tend to have defects of foreign matters, stains, etc. which involve food sanitary problems, and defects of checks, cracks scratches, seeds, and blisters Which may initiate breakages of the bottles. These defects have to be correctly detected so as to remove defective bottles. To this end there has been proposed a method for detecting these defects, based on a darkness distribution of an image formed by the transmitted light through a transparent or opaque bottle.
But this proposed method has a problem that a darkness distribution of a transmitted light image of the sidewall of a bottle is indicative of a light blocking defect of foreign matters, stains, etc., but is insufficient to indicate refractional defects of seeds, blisters, streaks, rumples, etc. Another problem of this method is that it is difficult to discriminate from a refractional defect a joint running lengthwise on the sidewall of a bottle which is formed inevitably when the bottle is formed.